staging/olpc_dcon: use s/r hooks from device_driver->pm

..instead of the i2c_driver hooks.  This should silence the following
runtime warnings:

[   17.820321] i2c-core: driver [olpc_dcon] using legacy suspend method
[   17.846082] i2c-core: driver [olpc_dcon] using legacy resume method

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>